This invention relates to an improved radiator cap for sealing the radiator of internal combustion engines and monitoring the liquid level in such radiators and warning when that liquid level is too low.
Previous attempts to monitor liquid levels involved using the tank cap on the reserve tank. Such reserve tank caps were equipped with a permanent magnet and reed switch with the reed switch adapted to detect the level of coolant in the reserve tank and thereby in the radiator through the position of the permanent magnet. The reserve tank functions to keep the pressure in the radiator at a predetermined value by feeding coolant into the radiator or by receiving an excess from the radiator through the radiator cap through the free expansion and contraction of the coolant. Therefore, to detect the decrease of coolant in the reserve tank is to detect the decrease of coolant in the radiator. However, the reed switch associated with the reserve tank cap cannot detect the decrease of the coolant when it is caused from various breakdowns of cooling systems, such as corrosion which could cause apertures within the radiator or coolant circuit. The interior or radiators would, under such a condition, be at an atmospheric pressure because of the aperture which would hold the vacuum-operated valve closed, thereby preventing the coolant from flowing back into the radiator and preventing accurate monitoring by the reserve tank system.